1. Field of the Invention
The present invention relates generally to spin valve sensors for magnetic heads, and more particularly to an improved tunnel valve MR sensor having a draped second magnetic shield.
2. Description of the Prior Art
Magnetic heads for hard disk drives typically have a read head portion including a magnetoresistive (MR) spin valve sensor structure for reading data from the disk of the hard disk drive. As is well known to those skilled in the art, such MR sensor structures include a plurality of thin film layers disposed between two magnetic shields that define the read gap. The thin film layers have particular magnetic properties, and are sensitive to the magnetic field of the data bits on the hard disk.
Recently developed read heads may use a tunnel junction sensor, also known as a “tunnel valve”, abbreviated “TV”, for reading the magnetic data bit signals from the hard disk. The TV sensor typically includes a nonmagnetic tunneling barrier layer sandwiched between a pinned magnetic layer and a free magnetic layer. The TV sensor is itself typically sandwiched between first and second magnetic shield layers that also serve as first and second electrical lead layers, and are connected to the tunnel junction sensor for conducting a tunneling current through it. The TV sensor is therefore configured to conduct Current Perpendicular to the Plane (CPP) of the film layers of the sensor. When reading data, a magnetic data bit of a hard disk will cause the direction of the magnetization of the free magnetic field layer to change, whereupon the electrical resistance of the sensor changes. This change in resistance affects the electrical current passing through the sensor, which is thus detected as a data signal.
Improved hard disk drives are manufactured with an ever increasing areal data storage density, which requires narrower and more closely spaced data tracks on the hard disk. As a result, the MR sensors must be fabricated with a reduced read track width, and stray magnetic shields from more closely spaced adjacent data tracks can generate noise in the sensor signals. In response MR sensors have been developed in which the second magnetic shield is draped around the MR sensor to provide magnetic shielding and thereby reduce the noise created from adjacent data tracks. Current methods to create such draped shield MR sensors have certain drawbacks, as described herebelow, which inhibit the reduction of the read track width of the sensor. The present invention provides a remedy for these problems.